I thought long and hard about this particular topic. If you first examine the law, 'scalping' as long as it is performed under certain circumstances is a perfectly legitimate service (see: ticket brokers), yet there are other examples too - amateur scalpers such as those outlined above in the case of the game consoles, and clearly illegitimate scalpers (at least in some countries) that stand outside events reselling for profit in spite of the law.
Morality is not the law though. In fact, there are sometimes clear distinctions where law - at least over here in the United Kingdom - does not strive for moral standing over an equitable one all the time. What then, decides if scalping is morally acceptable if not the laws that govern it?
Many others here have noted capitalism in some form or another, along with supply and demand. In these systems many businesses have thrived. Businesses are designed to make profit and appease shareholders, sometimes practicing methods generally considered underhanded or unethical. This is not about to turn into a 'Fight against the power' and 'Corporate hate' post, but ..
Lets look at exploitation. We've all heard about it, know about it, and even though sometimes it is tackled by well-meaning endeavours there isn't a whole lot of progress on that front and it undeniably exists to this day. Corporations need things made for cheap, the poor need some way to support themselves, cue exploitation and outsourcing. If we apply this idea that the businesses are providing something that is desired, though at a cutt-throat deal, it begins to resemble scalping.
Wait, what? Did you just compare third-world exploitation to scalping? This seems incredibly off-topic, but the essence I believe is the same. Exploitation of a desire, where you have the advantage and leverage it to get a deal which is not exactly fair.
Things get a little less clear when you apply this idea to luxuries. Though third-world exploitation is undeniably unfair, it still provides work and a living, and that is a necessity for life. When you do not 'need' something but pay for exorbant prices anyway, is that still exploitation or clever (if somewhat unkind) leveraging of supply and demand? Do these scalpers depend on their operation for a living? Does fair / unfair equate to good / evil to you, or simply superior strategy and mercantile?
Personally speaking, I think it begins to come down to your own stance on the matter. Is it okay for someone to make a quick buck at the expense of other people - either because other people would do the same or that they are simply exercizing initiative where others could? Does your decision change if that person is making a living out of it or this entity has an advantage in the matter where most others do not?
Rule of thumb: in my general sense of morality, exploitation of an advantage to the detriment of someone else is considered bad as I'm sure a few will agree. Scalping almost has vaguely similar connotations to blackmail when put that way. If someone really wanted something I had, I wouldn't go out of my way to make myself all the better for their need as that would be unfair, especially if they have no other way of obtaining said thing - if I was really good (charitable, generous, general definitions of benevolence) I'd make it available to them at the lowest 'price' possible to sustain myself or take the loss. If you believe in neutrality to be found in actions, making it available to them at the same price it would cost me would be 'acceptable' and would fall on neither side of the fence. Theoretically.
I can't really give you an answer. Though, I will say that generally speaking, most scalpers probably aren't the most saintly of people.
Regards,
MultiMasky